Method and apparatus of peer link setting, and method and apparatus of channel switching, in wireless mesh network

ABSTRACT

A method and apparatus for configuring mesh peer link and a method and apparatus for switching channel in wireless mesh network are provided. A method of configuring a mesh peer link in a wireless mesh network includes a first mesh station transmitting a mesh peering open frame to a second mesh station, and the first mesh station receiving a mesh peering confirm frame from the second mesh station in response to the mesh peering open frame, wherein the first mesh station and the second mesh station support a very high throughput (VHT), and wherein the mesh peering open frame and the mesh peering confirm frame comprise a VHT capability information element.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority to U.S.application Ser. No. 13/651,306, filed on Oct. 12, 2012, which claimsthe benefit of priority of Korean Patent Application No. 10-2011-0104860filed on Oct. 13, 2011, Korean Patent Application No. 10-2011-0114104filed on Nov. 3, 2011, Korean Patent Application No. 10-2012-0112825filed on Oct. 11, 2012, Korean Patent Application No. 10-2011-0104859filed on Oct. 13, 2011 and Korean Patent Application No. 10-2012-0112912filed on Oct. 11, 2012, all of which are incorporated by reference intheir entirety herein.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a mesh network, and more particularly,to a method of providing a very high throughput (VHT) wireless localarea network (LAN) technology.

Related Art

An IEEE 802.11s based mesh network supports direct communication of aplurality of wireless devices having a relay function not via an accesspoint (AP). In view of a function, a distribution system (DS) of an APmay be replaced by an interoperable wireless link or a multi-hop pathamong a plurality of APs. According to the mesh network, since apeer-to-peer wireless link in which one wireless device interacts withone or more adjacent wireless devices and/or APs may be configured,flexible wireless connection may be performed.

In the mesh network, one wireless device may be connected to a pluralityof other wireless devices to have a plurality of communication paths.The communication paths among the wireless devices are referred to aswireless mesh links, mesh peer links, or peer links. The wirelessdevices are referred to as mesh points (MP), however, are not limited tothe MPs. Among the MPs, MPs that perform the function of the AP as wellas the above-described relay function are referred to as mesh accesspoints (MAP).

The mesh network has advantages of flexibility in establishing thenetwork, reliability by a detour route, and reduction in powerconsumption in accordance with reduction in a communication distance.Specifically, a flexible network may be established among the MPs evenin a place where a communication network using the mesh network does notexist. In the mesh network, the plurality of MPs are connected to eachother so that a plurality of detour routes may be secured. Therefore,although one MP is out of order, data may be transmitted through otherpaths. In addition, in the mesh network, although the communicationcoverage of one MP is not large, since communication may be performedvia an adjacent MP, remote communication may be performed with lowpower.

An IEEE 802.11n wireless LAN technology is supported in the IEEE 802.11sbased mesh network. The IEEE 802.11n as a standard technology relativelyrecently established in order to overcome limitations on communicationspeed that is the weak point of a wireless LAN is designed to increasethe speed and reliability of a network and to extend the operationcoverage of a wireless network. Specifically, the IEEE 802.11n is basedon a multiple inputs and multiple outputs (MIMO) technology in which aplurality of antennas are adopted to a transmitter and/or a receiver inorder to support high throughput (HT) having data throughput of maximum600 Mbps, to minimize a transmission error, and to optimize a data rate.

As supply of the wireless LAN is activated and various applications usethe wireless LAN, recently, a new wireless LAN technology of supportinghigher throughput than data processing speed supported by the IEEE802.11n is required. As a succeeding technology of the IEEE 802.11n, anIEEE 802.11ac VHT wireless LAN technology of supporting VHT is newlysuggested. The VHT wireless LAN supports data processing speed of noless than 1 Gbps in an MAC service access point (SAP). The name of theVHT wireless LAN is arbitrary. In order to provide data throughput of noless than 1 Gbps, a reliability test for a VHT wireless LAN system inwhich 4×4 MIMO and 80 MHz channel bandwidth are used is being performed.

Therefore, a method of supporting the VHT wireless LAN technology in theIEEE 802.11s based mesh network is required.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a method of exchangingvery high throughput (VHT) capability information among mesh points (MP)in order to use a VHT wireless local access network (LAN) technology ina wireless mesh network.

Another object of the invention is to provide a method of using a widebandwidth channel switch function of no less than 80 MHz provided by theVHT wireless LAN technology in the wireless mesh network and a method ofcontrolling transmission power of VHT.

In an embodiment of the present invention, a method of configuring amesh peer link in a wireless mesh network is provided. The methodincludes a first mesh station transmitting a mesh peering open frame toa second mesh station and the first mesh station receiving a meshpeering confirm frame from the second mesh station in response to themesh peering open frame.

The first mesh station and the second mesh station may support a veryhigh throughput (VHT), and the mesh peering open frame and the meshpeering confirm frame may comprise a VHT capability information element.

The mesh peering open frame and the mesh peering confirm frame mayfurther comprise a VHT operation information element.

The first mesh station may perform passive scanning or active scanningin order to discover the second mesh station before transmitting themesh peering open frame.

The VHT capability information element may comprise at least one of aninformation element indicating a maximum MAC protocol data unit (MPDU)length, an information element indicating a channel bandwidth supportedby a station, an information element indicating whether an encodedpacket is received by a low density parity check (LDPC), informationelements indicating whether short guard intervals (GIs) are supported,an information element indicating whether reception of a PLCP protocoldata unit (PPDU) using space time block coding (STBC) is supported, andan information element indicating whether a transmission opportunity(TXOP) power save mode is supported.

The VHT operation information element may comprise at least one of aninformation element indicating an operation channel bandwidth and aninformation element defining a channel center frequency.

In another embodiment of the present invention, a wireless device forsupporting a method of configuring a mesh peer link in a wireless meshnetwork is provided. The wireless device includes a processor forgenerating and processing a frame and a transceiver connected to theprocessor to transmit and receive the frame generated by the processor.

The processor may generate a mesh peering open frame including a VHTcapability information element to transmit the generated mesh peeringopen frame to the wireless device and a neighbor mesh station, and theprocessor may receive a mesh peering confirm frame including the VHTcapability information element from the neighbor mesh station inresponse to the mesh peering open frame.

The mesh peering open frame and the mesh peering confirm frame mayfurther comprise a VHT operation information element.

In still another embodiment of the present invention, a channel switchmethod in a wireless mesh network is provided. The method includes afirst mesh station that is to be switched from a first channel to asecond channel transmits a channel switch announcement frame to a secondmesh station.

The first mesh station and the second mesh station may support a VHT,and the channel switch announcement frame may comprise a wide bandwidthchannel switch element field and a mesh channel switch parameter elementfield.

The wide bandwidth channel switch element field may indicate performingswitch to a channel bandwidth larger than 40 MHz.

The mesh channel switch parameter element field may indicate performingswitch from the first channel to the second channel in the wireless meshnetwork.

In still another embodiment of the present invention, a wireless devicefor supporting a channel switch method in a wireless mesh network isprovided. The wireless device includes a processor for generating andprocessing a frame and a transceiver connected to the processor totransmit and receive the frame generated by the processor.

When the wireless device performs switch from a first channel to asecond channel, the processor may generate a channel switch announcementframe including a wide bandwidth channel switch element field and a meshchannel switch parameter element field.

The wide bandwidth channel switch element field may indicate performingswitch to a channel bandwidth larger than 40 MHz, and the mesh channelswitch parameter element field may indicate performing switch from thefirst channel to the second channel in the wireless mesh network.

In still another embodiment of the present invention, a method ofdetermining maximum transmit power in a wireless mesh network isprovided. The method includes a mesh station determines regulatorymaximum transmit power (RMTP) regulated by each country for a currentlyused channel, the RMTP is a smaller value between first RMTP obtained bya country element received from a neighbor mesh station of the wirelessmesh network or stations of other wireless LAN systems and second RMTPfor a channel in a current regulatory domain, the mesh stationdetermines local maximum transmit power (LMTP) for the currently usedchannel, and the LMTP is the smallest value among first LMTP obtained bya country element and a power constraint element received from aneighbor mesh station of the wireless mesh network or stations of otherwireless LAN systems, second LMTP obtained by a VHT transmit powerenvelope element and an extended power constraint element received froma neighbor mesh station of the wireless mesh network or stations ofother wireless LAN systems, and third LMTP for a channel in a currentregulatory domain known from other sources.

The mesh station may publish the RMTP using the country element througha beacon frame and a probe response frame.

The mesh station may publish the LMTP using combination of the countryelement and the power constraint element or combination of the VHTtransmit power envelope element and an extended power constraint elementthrough the beacon frame and the probe response frame.

In the wireless mesh network, VHT wireless LAN based wirelesstransmission may be performed among the MPs and the wide bandwidthchannel switch function of the VHT wireless LAN may be provided.Therefore, it is possible to provide better performance than theconventional wireless mesh network.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view illustrating an example of a wireless mesh networkaccording to an embodiment of the present invention.

FIG. 2 is a message flowchart illustrating a mesh peer link configuringprocess according to an embodiment of the present invention.

FIG. 3 is a view illustrating an example of information items includedin the mesh peering open frames used for the mesh peer link configuringprocess according to the embodiment of the present invention.

FIG. 4 is a view illustrating an example of information items includedin the mesh peering confirm frames used for the mesh peer linkconfiguring process according to the embodiment of the presentinvention.

FIG. 5 is a view illustrating an example of fields included in the VHTcapability information element according to the embodiment of thepresent invention.

FIG. 6 is a view illustrating an example of the fields included in theVHT operation information according to the embodiment of the presentinvention.

FIG. 7 is a view illustrating a format of the channel switchannouncement frame for supporting the wide bandwidth channel switchfunction according to an embodiment of the present invention.

FIG. 8 is a view illustrating a mesh BSS to which transmit power controlis applied.

FIG. 9 is a block diagram illustrating a wireless device according to anembodiment of the present invention.

FIG. 10 is a flowchart illustrating a method of providing the TXOP PSmode of the mesh STAs according to the embodiment of the presentinvention.

FIG. 11 is a view illustrating an example a VHT operating mode fieldincluded in a VHT operating mode notification frame for changing theTXOP PS mode according to an embodiment of the present invention.

FIG. 12 is a view illustrating the fields of a PS mode subelementincluded in a diagnostic information subelement for reportinginformation on the TXOP PS mode according to an embodiment of thepresent invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, some embodiments of the present invention are described indetail with reference to the accompanying drawings in order for thoseskilled in the art to be able to readily implement the invention.Furthermore, the present invention is not limited to the followingembodiments and may be modified in various ways within the scope of thetechnical spirit of the present invention.

Elements described in this specification may include additional elementsother than elements to be described later, at need, and a detaileddescription of parts not directly related to the present invention orredundant parts is omitted. Furthermore, when it is said that any partincludes (or comprises) any element, it means the part does not excludeother elements and may further include other elements.

FIG. 1 is a view illustrating an example of a wireless mesh networkaccording to an embodiment of the present invention.

Referring to FIG. 1 , a wireless mesh network includes one or aplurality of stations (STA) 131, 132, 133, and 134 and one or morewireless devices, that is, mesh points (MP) 111, 121, 122, and 123.Among the MPs, since the MPs 121 and 122 have the STAs 131, 132, 133,and 134 associated therewith, the MPs 121 and 122 become mesh accesspoints (MAP) for simultaneously performing a function of access points(AP). The MP 111 wiredly or wirelessly connected to an external networkis referred to as a mesh portal.

The STAs 131 to 134 as arbitrary functional media including mediumaccess control (MAC) according to the regulation of the IEEE 802.11standard and physical layer interface for wireless media are non-APstations. The STAs 131 to 134 inform the MAP 121 or 122 associatedtherewith of multicast subscription information thereon. The STAs may bereferred to as wireless transmit/receive units (WTRU), user equipments(UE), mobile stations (MS), or mobile subscriber units as well aswireless stations.

The MPs 111, 121, 122, and 123 as media for establishing the wirelessmesh network are one of the functional media of the IEEE 802.11including the MAC according to the regulation of the IEEE 802.11standard and the physical layer interface. The MPs 111, 121, 122, and123 are wireless devices supporting mesh services. The mesh servicesinclude various services by which direct communication may be performedamong the MPs that form the mesh network. Communication between the twoMPs for providing the mesh services, for example, the MPs 121 and 123 isperformed through a mesh link or a peer link that is a direct linkconfigured between the two MPs. According to the embodiment of thepresent invention, the MPs 111, 121, 122, and 123 support one or moreVHT MACs and PHY features so that VHT of no less than 1 Gbps may beachieved.

Among the MPs 111, 121, 122, and 123, the MPs that perform the functionof the APs are referred to as the MAPs. Therefore, the MAPs 121 and 122perform the function of the APs for associated stations configured to beconnected thereto as well as the function of the above-described MPs.The APs may be referred to as aggregation controllers, base stations(BS), node-Bs, or site controllers.

In the wireless mesh network illustrated in FIG. 1 , an independentnetwork formed of the MPs 111, 121, 122, and 123 for supporting the meshservices is referred to as a mesh basic service set (BSS). The BSS is aset of STAs that may communicate with each other in successfulsynchronization and is not a concept referring to a specific region. TheMPs 111, 121, 122, and 123 in the mesh BSS may be referred to as a meshSTA.

The mesh BSS may be wiredly or wirelessly connected to an externalnetwork to form a wireless LAN system. For example, the mesh BSS may beconnected to a network such as an infrastructure BSS and an independentBSS (IBSS) to communicate with the network.

The infrastructure BSS includes one or more non-AP STAs, an access pointas an STA that provides a distribution service, and a distributionsystem (DS) for connecting a plurality of access points. In theinfrastructure BSS, the AP STA manages the non-AP STAs of the BSS.Meanwhile, the IBSS operates in an ad-hoc mode. Since the IBSS does notinclude an AP, there is no centralized management entity that performs amanagement function in the center. That is, in the IBSS, the non-AP STAsare managed in a distributed manner. In the IBSS, all of the STAs may beformed of mobile stations and form a self-contained network since accessto the DS is not allowed.

In order to provide very high speed wireless transmission of no lessthan 1 Gbps using a VHT wireless LAN technology in the mesh BSS,information indicating whether the MPs (hereinafter, referred to as meshSTAs) that form the mesh BSS according to the embodiment of the presentinvention are the mesh STAs supporting a VHT wireless LAN function is tobe exchanged. In addition, the mesh STAs must be able to transmit andreceive data using a wide bandwidth channel of no less than 80 MHzprovided by the VHT wireless LAN technology. Hereinafter, methods inwhich the mesh STAs may use the VHT wireless LAN technology in theabove-described mesh BSS will be described in detail with reference tothe embodiment.

FIG. 2 is a message flowchart illustrating a mesh peer link configuringprocess according to an embodiment of the present invention. The meshpeer link configuring process of FIG. 2 is performed after performing amesh discovery process.

In the mesh discovery process, a mesh STA that desires to configure apeer link with another mesh STA searches a candidate mesh STA that maybe a peer mesh STA or a neighbor mesh STA. Here, a mesh STA that formsthe mesh BSS has a predetermined mesh profile. Therefore, a meshsearching process is a process of searching mesh STAs whose meshprofiles coincide with each other or whose mesh profiles may coincidewith each other. A mesh profile includes a mesh identifier, a pathselection protocol identifier, a path selection metric identifier, and acongestion control mode identifier.

Two methods are used for the mesh searching process. In a passive scanmethod as the first method, a mesh beacon frame transmitted from anothermesh STA is used. That is, a mesh STA that desires to participate in themesh BSS receives a mesh beacon frame periodically transmitted fromanother mesh STA to search a candidate mesh STA that desires to performpeering. In an active scan method as the second method, a mesh STA thatdesires to participate in the mesh BSS first transmits a mesh proberequest frame. The mesh STA that receives the mesh probe request frametransmits a mesh probe response frame to a transmission mesh STA whenthe mesh STA desires to configure a peer link with the transmission meshSTA.

Mesh ID information is included in the mesh beacon frame or the meshprobe request/response frames. Mesh configuration information isincluded in the mesh beacon frame or the mesh probe response frame. Amesh STA that desires to configure a peer link may know mesh profileinformation of another mesh STA (a mesh STA that transmits the meshbeacon frame or a mesh STA that transmits the mesh response frame) usingthe mesh ID information and the mesh configuration information. Inparticular, the mesh configuration information is used for graspinginformation items other than the mesh ID information among theinformation items that form the mesh profile.

When neighbor mesh STAs are searched through the above-described meshsearching process, the mesh STA desires to configure a mesh link withthe searched neighbor mesh STAs. In a mesh link configuring process, alogic link is configured among mesh STAs. The mesh link configuringprocess may be referred to as a peering process. In the mesh BSS, a peerlink is configured through the peering process. A data frame may betransmitted and received only among the mesh STAs where the peer link isconfigured. In order to configure the mesh peer link among the meshSTAs, a mesh peering open frame and a mesh peering confirm frame aretransmitted and received.

Referring to FIG. 2 , a process of a first mesh STA 10 and a second meshSTA 20 configuring a peer link will be described.

The first mesh STA 10 transmits a first mesh peering open frame to thesecond mesh STA 20 and receives a first mesh peering confirm frame fromthe second mesh STA 20 in response to the first mesh peering open frame.The second mesh STA 20 transmits a second mesh peering open frame to thefirst mesh STA 10 and receives a second mesh peering confirm frame fromthe first mesh STA 10.

There are no limitations on the order of transmitting and receiving thefirst mesh peering open/confirm frames and the second mesh peeringopen/confirm frames. For example, the first mesh STA 10 may transmit thefirst mesh peering open frame before or after receiving the second meshpeering open frame from the second mesh STA 20 and may transmit thesecond mesh peering open frame before or after transmitting the secondmesh peering confirm frame to the second mesh STAs 20 in response to thereceived second mesh peering open frame.

According to the embodiment of the present invention, information oncapability of a wireless device related to the VHT service, that is, VHTcapability information is included in the first and second mesh peeringopen frames and the first and second mesh peering confirm framestransmitted and received by the first mesh STA 10 and the second meshSTA 20. That is, information on capability related to the VHT wirelessLAN function supported by the mesh STA is included in the mesh peeringopen frames and the mesh peering confirm frames used when the peer linkis configured in the mesh BSS.

FIG. 3 is a view illustrating an example of information items includedin the mesh peering open frames used for the mesh peer link configuringprocess according to the embodiment of the present invention. Asdescribed above, the mesh peering open frame is used for starting themesh link configuring process.

The mesh peering open frames according to the present invention includeall of the mesh peering open frame action field articles of the IEEE802.11s, for example, category information, action value information,capability information, and supported rate information. In addition,when a predetermined condition is satisfied, extended support rateinformation, power capability information, supported channelinformation, robust security network (RSN) information, mesh IDinformation, mesh configuration information, mesh peering managementinformation, and message integration code (MIC) information may beincluded.

In addition, when the mesh STA that supports the mesh peering openframes supports the VHT function, as illustrated in FIG. 3 , a VHTcapability information element and a VHT operation information elementare included in the mesh peering open frames.

The VHT capability information element is for the mesh STA informing theopponent mesh STA that the mesh STA supports VHT MAC/PHY and for themesh STA informing the opponent mesh STA of VHT capabilities supportedthereby. The VHT operation information element is for the mesh BSScontrolling the operation of the mesh STA that supports the VHT wirelessLAN.

The order or number of fields of the VHT capability information and theVHT operation information illustrated in FIG. 3 is an example and theorder or number of the fields may be changed as occasion demands.

FIG. 4 is a view illustrating an example of information items includedin the mesh peering confirm frames used for the mesh peer linkconfiguring process according to the embodiment of the presentinvention. As described above, the mesh peering confirm framestransmitted in response to the received mesh peering open frames areused to confirm mesh peering.

The mesh peering confirm frames according to the present inventioninclude all of the mesh peering confirm frame action field articles ofthe IEEE 802.11s, for example, a category information element, an actionvalue information element, a capability information element, anassociation identifier (AID) information element, and a supported rateinformation element. When a predetermined condition is satisfied, anextended support rate information element, a robust security network(RSN) information element, a mesh ID information element, a meshconfiguration information element, a mesh peering management informationelement, and a MIC information element may be included.

In addition, when the mesh STA that supports the mesh peering confirmframes supports the VHT function, as illustrated in FIG. 4 , VHTcapability information element and VHT operation information element areincluded in the mesh peering confirm frames.

The VHT capability information element is for the mesh STA informing theopponent mesh STA that the mesh STA supports the VHT MAC/PHY and for themesh STA informing the opponent mesh STA of the VHT capabilitiessupported thereby. The VHT operation information element is for the meshBSS controlling the operation of the mesh STA that supports the VHTwireless LAN.

The order or number of fields of the VHT capability information and theVHT operation information illustrated in FIG. 4 is an example and theorder or number of the fields may be changed as occasion demands.

Hereinafter, the structures the fields of the VHT capability informationelement and the VHT operation information element included in the meshpeering open frames and the mesh peering confirm frames to betransmitted will be described. The names and order of the fieldsincluded in the VHT capability information element and the VHT operationinformation element are arbitrary. The present invention is not limitedto the names of the fields and the order of the fields.

FIG. 5 is a view illustrating an example of fields included in the VHTcapability information element according to the embodiment of thepresent invention.

Referring to FIG. 5 , a VHT capability information element 400 includesa maximum MAC protocol data unit (MPDU) length 411 indicating maximumMPDU length, a supported channel width set 412 indicating a channelbandwidth supported by a STA, an Rx low density parity check (LDPC) 413indicating whether an encoded packet is received by an LDPC, short guardintervals (GI) 414 and 415 indicating whether short GIs are supported, aTx space time block coding (STBC) 416 indicating whether transmission ofat least 2×1 STBC is supported, an Rx STBC 417 indicating whetherreception of a PLCP protocol data unit (PPDU) using the STBC issupported, an SU beamformer capable 418 indicating whether an operationof SU beamformer is supported, an SU beamformee capable 419 indicatingwhether an operation of SU beamformee is supported, a compressedsteering number of beamformer antennas supported 420 indicating themaximum number of beamformer antennas supported in the SU beamformeecapable, a number of sounding dimensions 421 indicating the maximumvalue of TXVECTOP parameter NUM_STS in the SU beamformer capable, an MUbeamformer capable 422 indicating whether an operation of MU beamformeris supported, an MU beamformee capable 423 indicating whether anoperation of MU beamformee is supported, a VHT transmission opportunity(TXOP) PS 424 indicating whether an AP supports a VHT TXOP power savemode or whether a non-AP STA is the VHT TXOP power save mode, a +HTC-VHTcapable 425 indicating whether an STA supports reception of a VHTmodified HT control field, a maximum A-MPDU length exponent 426indicating the maximum length of A-MPDU supported by the STA, a VHT linkadaptation capable 427 indicating whether the STA supports linkadaptation using the VHT modified HT control field, an Rx antennapattern consistency 428 indicating whether an Rx antenna pattern may bechanged, and a Tx antenna pattern consistency 429 indicating whether aTx antenna pattern may be changed.

All of the fields that may be included in the above-described VHTcapability information element 400 are included or some of the fieldsmay be included as occasion demands.

FIG. 6 is a view illustrating an example of the fields included in theVHT operation information according to the embodiment of the presentinvention.

Referring to FIG. 6 , a VHT operation information element 500 mayinclude at least one of a channel width 511 indicating an operationchannel bandwidth, a channel center frequency segment 0 512 defining achannel center frequency for a 80 MHz or 160 MHz VHT BSS and a segment 0channel center frequency for a 80+80 MHz VHT BSS, and a channel centerfrequency segment 1 513 defining a segment 1 channel center frequencyfor the 80+80 MHz VHT BSS.

The fields that may be included in the above-described VHT operationinformation element 500 may be included or some of the fields may beincluded.

In the conventional 802.11s based mesh BSS, although mesh STAs(hereinafter, referred to as VHT mesh STAs) that support the VHTwireless LAN function exist, information on whether the VHT services aresupported among the mesh STAs and information on VHT capabilitysupported by a corresponding STA may not be exchanged. However, the VHTmesh STAs according to the embodiment of the present invention mayexchange VHT service information items when the mesh peer link isconfigured. That is, as illustrated in FIGS. 3 and 4 , a functioncorresponding to a subset of VHT features is used among the VHT meshSTAs that configure mesh peering by extending the mesh peering openframes and the mesh peering confirm frames.

On the other hand, when the mesh STAs that form the mesh peer link orthat desire to form the mesh peer link in the mesh BSS desire to changechannels, it is necessary to inform a peer mesh STA that the mesh STAsthat form the mesh peer link or that desire to form the mesh peer linkin the mesh BSS desire to change channels. When communication isperformed through the peer link like in the mesh BSS, communication maybe performed only among mesh STAs having the same channel. Therefore,when a mesh STAS that desires to change a channel does not inform thepeer mesh STA that the mesh STA desires to change the channel, the peerlink of the peer mesh STA is unilaterally canceled by the mesh STA.Therefore, when the mesh STA desires to change the channel, first, themesh STA preferably informs the peer mesh STA that the mesh STA desiresto change the channel so that the peer mesh STA may determine whether tocontinuously maintain the peer link or to cancel the peer link.Therefore, in order for the mesh STA that desires to change the channelto inform the peer mesh STA that the mesh STA desires to change thechannel, a channel switch announcement frame is transmitted to the peermesh STA.

When the VHT mesh STA according to the embodiment of the presentinvention desires to change the channel, a channel bandwidth of no lessthan 80 MHz provided by an 802.11ac VHT wireless LAN technology must beable to be used. Therefore, according to the embodiment of the presentinvention, information items for supporting a wide bandwidth channelswitch function to the channel switch announcement frame when the VHTmesh STA is changed into a new channel are included.

FIG. 7 is a view illustrating a format of the channel switchannouncement frame for supporting the wide bandwidth channel switchfunction according to an embodiment of the present invention. Thechannel switch announcement frame is used for informing that the AP inthe BSS or the mesh STA in the mesh BSS is changed into a new channel.

Referring to FIG. 7 , a channel switch announcement frame 300 includes acategory field 310, an action field 320, a channel switch announcementelement field 330, and a secondary channel offset element field 340.

The category field 310 may include a value indicating a category towhich the channel switch announcement frame 300 belongs, for example, amanagement category. The action field 320 may include a value indicatingdetailed action content according to the channel switch announcementframe 300, for example, spectrum management action. The channel switchannouncement element field 330 used by mesh STAs in the mesh BSS toinform other mesh STAs when the mesh STAs are changed into new channelsmay include the numbers of new channels and a priority value determinedby associations of the new channels. The secondary channel offsetelement field 340 for designating a secondary channel number in achannel to be changed may specify a secondary channel using a relativeposition with respect to a primary channel.

When the VHT mesh STA according to the embodiment of the presentinvention desires to change the channel, as illustrated in FIG. 7 , thechannel switch announcement frame 300 includes a mesh channel switchparameter element field 350 and a wide bandwidth channel switch elementfield 360.

The mesh channel switch parameter element field 350 for supporting achannel switch in the mesh BSS is included when the VHT mesh STA ischanged from a first channel into a second channel in the mesh BSS. Whenthe VHT mesh STA is changed into another channel excluding the mesh BSS,the mesh channel switch parameter element field 350 is not included inthe channel switch announcement frame 300.

The wide bandwidth channel switch element field 360 for supporting thewide bandwidth channel switch of the VHT wireless LAN technology informsother mesh STAs that the VHT mesh STA is switched to a channel bandwidthlarger than 40 MHz. That is, when the VHT mesh STA is changed into achannel bandwidth larger than 40 MHz, the wide bandwidth channel switchelement field 360 may be included in the channel switch announcementframe 300.

The channel switch announcement frame 300 according to the embodiment ofthe present invention may further include a new VHT transmit powerenvelope element field 370. The new VHT transmit power envelope elementfield 370 may be formed to have the same type as a conventional VHTtransmit power envelope element and includes a unique value of localmaximum transmit power (LMTP) units interpretation. LMTP is the maximumtransmit power that may be used by a corresponding BSS.

The new VHT transmit power envelope element field 370 indicates LMTP forthe BSS of a bandwidth designated by designated units interpretationafter changing a channel.

The order of the fields in the channel switch announcement frame 300illustrated in FIG. 7 , the number of octets of the fields, and thelengths of the fields are only an example. The order of the fields andthe lengths of the fields may vary as occasion demands. In addition, thechannel switch announcement frame 300 may further include fields otherthan the fields illustrated in FIG. 7 as occasion demands or do notalways include the fields illustrated in FIG. 7 .

Using the channel switch announcement frame according to the embodimentof the present invention, although the VHT mesh STA changes the channelas occasion demands, it is guaranteed so that a bandwidth of no lessthan 80 MHz may be used. Therefore, it is possible to obtain improvedperformance in the mesh BSS according to the present invention.

The mesh BSS according to the embodiment of the present inventioncontrols transmit power for a currently used channel to reduceinterference with other networks, for example, a BSS, an IBSS, and apersonal basic service set (PBSS) and to support the bandwidth of noless than 80 MHz. Therefore, the mesh STA adaptively controls transmitpower to efficiently manage radio wave resource, to reduce powerconsumption of the mesh STA, and to reduce consumption of a battery.

FIG. 8 is a view illustrating a mesh BSS to which transmit power controlis applied.

Referring to FIG. 8 , the mesh BSS to which the transmit power controlis applied may be divided into three transmit power ranges of regulatorymaximum transmit power (RMTP), LMTP, and current transmit power (CTP).

The RMTP is the maximum transmit power regulated by each country.

The LMTP is the maximum transmit power that may be used for acorresponding mesh BSS and is configured as a smaller value than theRMTP in order to limit the maximum output of the corresponding mesh BSSand to protect other radio wave shared systems.

Current transmit power used among the mesh STAs is configured as a valuesmaller than or equal to the LMTP.

In the above-described transmit power control method, a mesh STAdetermines RMTP and LMTP for a currently used channel using the beaconframe and the probe response frame transmitted and received among themesh STAs so that the maximum transmit power is controlled. In addition,according to the present invention, the maximum transmit power iscontrolled using a VHT transmit power envelope element and an extendedpower constraint element in order to provide a large channel bandwidthsupported by the VHT wireless LAN.

Hereinafter, a method of the mesh STA determining the RMTP and the LMTPto control the maximum transmit power according to the embodiment of thepresent invention will be described in detail.

The mesh STA determines a smaller RMTP value between (i) and (ii) as anRMTP value for the currently used channel.

-   -   (i) RMTP obtained by a country element received from a neighbor        mesh STA of the mesh BSS or STAs (for example, an AP in the BSS,        a PBSS central point (PCP) in the PBSS, and other STAs in the        IBSS) of other wireless LAN systems    -   (ii) RMTP for a channel in a current regulatory domain known        from other sources

The mesh STA determines the smallest LMTP value among (i), (ii), and(iii) as the LMTP value for the currently used channel.

-   -   (i) LMTP obtained by a country element and a power constraint        element received from a neighbor mesh STA of the mesh BSS or        STAs (for example, an AP in the BSS, a PCP in the PBSS, and        other STAs in the IBSS) of other wireless LAN systems    -   (ii) LMTP obtained by a VHT transmit power envelope element and        an extended power constraint element received from a neighbor        mesh STA of the mesh BSS or STAs (for example, an AP in the BSS,        a PCP in the PBSS, and other STAs in the IBSS) of other wireless        LAN systems    -   (iii) LMTP for the channel in a current regulatory domain known        from other sources

Here, the country element is information indicating that transmit poweris regulated by frequency bandwidth in each country. The powerconstraint element is for regulating the LMTP. The VHT transmit powerenvelope element indicates the maximum transmit power for variouschannel bandwidth of the VHT mesh STA. The extended power constraintelement defines LMTP for each channel bandwidth.

In the above, the method of the mesh STA in the mesh BSS determining theRMTP and the LMTP is described. However, the present invention is notlimited to the above. For example, the present invention may be appliedto an STA in the BSS, an STA in the IBSS, and a PCP in the PBSS.

On the other hand, the mesh STA must publish the RMTP for the currentlyused channel determined in the above, that is, an operating channelusing the country element through the beacon frame and the proberesponse frame.

In addition, the mesh STA must publish the LMTP for the currently usedchannel determined in the above, that is, the operating channel usingone of combination of the country element and the power constraintelement and combination of the VHT transmit power envelope element andthe extended power constraint element through the beacon frame and theprobe response frame.

Here, STAs in other wireless systems such as an AP in the BSS and a STAin the IBSS as well as the mesh STA may publish the RMTP and the LMTPdetermined by the above-described transmit power control method throughthe beacon frame and the probe response frame.

The RMTP and the LMTP determined by the above-described transmit powercontrol method may be changed in a period where the mesh BSS and theinfrastructure BSS exist. However, how often and much the maximum valuechanges is to be determined in consideration of the stability of anetwork. The RMTP and the LMTP are not changed in a period where theIBSS exists.

In the VHT mesh STA according to the embodiment of the presentinvention, a mesh control field is included in a data frame in order toprovide a mesh function. The maximum length of the frame body of the VHTmesh STA is calculated in consideration of the length of the meshcontrol field.

FIG. 9 is a block diagram illustrating a wireless device according to anembodiment of the present invention. The wireless device may be the meshSTA.

Referring to FIG. 9 , a wireless device 30 includes a processor 32, amemory 34, and a transceiver 36.

The transceiver 36 transmits/receives a radio signal to realize thephysical layer of the IEEE 802.11. For example, a physical layersupporting the VHT may be realized.

The processor 32 is functionally connected to the transceiver 36 torealize the MAC layer of the IEEE 802.11.

The processor 32 generates and transmits the mesh peering open/confirmframes including the VHT capability information element and the VHToperation information element suggested by the present invention orinterprets the field values of the VHT capability information elementand the VHT operation information element included in the received meshpeering open/confirm frames so that the wireless device 30 may supportthe VHT function.

The processor 32 generates and transmits the channel switch announcementframe including the wide bandwidth channel switch element and the meshchannel switch parameter element to support the wide bandwidth channelswitch function suggested by the present invention.

The processor 32 may be realized to determine the RMTP and the LMTP forthe currently used channel suggested by the present invention and tocontrol the maximum transmit power.

That is, the processor 32 may be configured to realize theabove-described embodiments of the present invention.

The processor 32 and/or the transceiver 36 may include anapplication-specific integrated circuit (ASIC), another chip set, alogic circuit, and/or a data processing device. The memory 34 mayinclude a read only memory (ROM), a random access memory (RAM), a flashmemory, a memory card, a storage medium, and/or another storage device.When the embodiments are realized by software, the above-describedmethod may be realized by a module (a process and a function) thatperforms the above-described function. The module may be stored in thememory 34 and may be executed by the processor 32. The memory 34 may bein or outside the processor 32 and may be connected to the processor 32by various well-known means.

On the other hand, the architecture of a medium access control (MAC)secondary layer includes a distributed coordination function (DCF), apoint coordination function (PCF), and a hybrid coordination function(HCF). The HCF includes a contention based channel access methodreferred to as enhanced distributed channel access (EDCA) and anon-contention based channel access method referred to as HCF controlledchannel access (HCCA). In the EDCA mechanism, contention may beperformed in order to obtain a TXOP. That is, the MPs or the STAs obtainthe TXOP when EDCA contention is successful. The TXOP may be allotted bya hybrid coordinator (HC).

When a specific MP or a specific STA has a right to initiatetransmission to a wireless medium, the TXOP is used to provide andguarantee uniform time for which the specific MP or the specific STA maytransmit a frame at intervals where the right continues.

The STA that supports the IEEE 802.11 standard may be in one of an awakestate where the STA receives power enough to perform all of thefunctions including a function of transmitting/receiving a frame and adoze state or a sleep state where the STA uses a low amount of powerinstead of constraining the function of transmitting/receiving the framein order to manage its power.

The STA may be in an active mode and a power save (PS) mode in order tomanage power. In the active mode, the STA operates in the awake state.In the PS mode, the STA operates to reduce the use of power by beingswitched between the awake state and the doze state as occasion demands.For example, in the case where the STA is in the PS mode, the STA may bein the doze state to minimize the use of power when the STA does nottransmit the frame to/receive the frame from the AP or another STA. Whenit is necessary for the STA to transmit the frame or the STA isrequested to receive the frame, the STA enters the awake state totransmit/receive the frame and may return to the doze state aftercompleting transmitting/receiving the frame.

That is, the STA may operate in the PS mode in a TXOP period by beingswitched between the awake state and the doze state. Hereinafter, indescribing the present invention, the STA operating in the TXOP periodby being switched between the awake state and the doze state is referredto as a TXOP PS mode.

The conventional TXOP PS mode is limited to being applied only totransmission from the AP to the STA. It is indicated whether the APallows the TXOP PS mode or whether the STA is in the TXOP PS modethrough association between the AP and the STA. On the other hand, inthe mesh network illustrated in FIG. 1 , since not the association butthe peer link is performed among the MPs, the TXOP PS mode may not beused. Therefore, according to the present invention, a method, in whichinformation on the TXOP PS mode may be exchanged among the MPs(hereinafter, referred to as mesh STAs) during the peer link so that theTXOP PS mode of the mesh STAs may be applied in the wireless meshnetwork, is provided.

FIG. 10 is a flowchart illustrating a method of providing the TXOP PSmode of the mesh STAs according to the embodiment of the presentinvention.

FIG. 10 illustrates processes of a first mesh STA 10 and a second meshSTA 20 configuring the peer link to operate in the TXOP PS mode. A meshpeering open frame is used to initiate a mesh peer link procedure. Amesh peering confirm frame as a frame transmitted in response to thereceived mesh peering open frame is used to confirm mesh peering.

Referring to FIG. 10 , the first mesh STA 10 transmits the mesh peeringopen frame to the second mesh STA 20 (S200) and receives the meshpeering confirm frame from the second mesh STA 20 in response to themesh peering open frame (s210).

The second mesh STA 20 may transmit the mesh peering open frame to thefirst mesh STA 10 and may receive the mesh peering confirm frame fromthe first mesh STA 10 in response to the mesh peering open frame.

According to the embodiment of the present invention, information on theTXOP PS mode is included in the mesh peering open frame and the meshpeering confirm frame that the first mesh STA 10 and the second STA 20transmit and receive. That is, a VHT TXOP PS bit in a VHT capabilityinformation field provided in the IEEE 802.11ac standard is included.Whether the first mesh STA 10 and the second mesh STA 20 allow the TXOPPS mode and whether the first mesh STA 10 and the second mesh STA 20 usethe TXOP PS mode are indicated using the VHT TXOP PS bit.

In the case where the value of the VHT TXOP PS bit in the VHT capabilityinformation field is configured to indicate that the TXOP PS mode isallowed when the first mesh STA 10 transmits the mesh peering open frameand is configured to indicate that the TXOP PS mode is used when thesecond mesh STA 20 transmits the mesh peering confirm frame, when thefirst mesh STA 10 transmits a data frame in the TXOP period (S220), thesecond mesh STA 20 determines whether to receive the data frame (S230).

For example, the second mesh STA 20 may confirm a partial addressidentifier (AID) included in the data frame, that is, a receiver address(RA) to determine whether the data frame is transmitted thereto. Whenthe RA included in the data frame is the RA of the second mesh STA 20,the second mesh STA 20 is switched to the awake state to receive thedata frame. When the RA included in the data frame is not the RA of thesecond mesh STA 20, the second mesh STA 20 operates in the doze state inthe TXOP period. Here, since the partial AID is defined by the MACaddress of a receiver, the receiver of the data frame may be identified.Therefore, when the mesh STAs according to the embodiment of the presentinvention operate in the TXOP PS mode, the partial AID of the receiveddata frame is confirmed in a physical layer so that power may be savedin the physical layer.

The mesh peering open frame according to the present invention furtherincludes the VHT capability information elements including the VHT TXOPPS field that indicates whether the mesh STAs allow the TXOP PS mode andwhether the mesh STAs use the TXOP PS mode as illustrated in FIG. 3 .The order numbers of the VHT capability information elements illustratedin FIG. 3 are only an example and may vary as occasion demands.

In addition, the mesh peering confirm frame according to the presentinvention further includes the VHT capability information elementsincluding the VHT TXOP PS field that indicates whether the mesh STAsallow the TXOP PS mode and whether the mesh STAs use the TXOP PS mode asillustrated in FIG. 4 . The order numbers of the VHT capabilityinformation elements illustrated in FIG. 4 are only an example and mayvary as occasion demands.

Here, the VHT capability information elements included in the meshpeering open frame and the mesh peering confirm frame may be configuredas illustrated in FIG. 5 and whether the mesh STAs allow the TXOP PSmode and whether the mesh STAs use the TXOP PS mode may be indicatedusing the VHT TXOP PS field 424 in the VHT capability informationelements.

As described above, the mesh STAs according to the embodiment of thepresent invention transmit and receive the mesh peering open frame andthe mesh peering confirm frame with information on the TXOP PS modethereof during the configuration of the peer link so that the power ofthe mesh STAs may be saved. However, when the mesh STAs desire to changethe TXOP PS mode after configuring the peer link, for example, when themesh STAs do not operate in the TXOP PS mode and desire to be switchedto the TXOP PS mode with reduction in the amount of power of a batteryor operate in the TXOP PS mode and desire to deviate from the TXOP PSmode in order to increase transmission efficiency, the peer link must beconfigured again.

Hereinafter, in order to solve the above-described problem, a method ofdynamically changing the TXOP PS mode will be described.

FIG. 11 is a view illustrating an example a VHT operating mode fieldincluded in a VHT operating mode notification frame for changing theTXOP PS mode according to an embodiment of the present invention.

The VHT operating mode notification frame is used for the STA thattransmits the VHT operating mode notification frame to notify other STAsof an operating channel width and/or the number of spatial streams (SS)that the STA may receive.

According to the present invention, the VHT operating mode field 200 inthe VHT operating mode notification frame illustrated in FIG. 11 isextended to notify a change in the TXOP PS mode among the mesh STAs.

Referring to FIG. 11 , the VHT operating mode field 200 in the VHToperating mode notification frame includes a channel width field 210 forindicating an operating channel width, a reserved field 220, a TXOP PSmode field 230 for indicating whether the STA is in the PS mode, an RxNss field 240 for indicating the number of SSs (spatial streams) thatthe transmitting STA may receive, and a Max Nss for SU present field 250for indicating the maximum number of SSs for SU.

When the mesh STAs in the wireless mesh network according to theembodiment of the present invention desire to change the TXOP PS modeafter configuring the peer link, whether the TXOP PS is allowed andwhether the TXOP PS mode is used may be changed using the bit value ofthe TXOP PS mode 230 in the VHT operating mode field 200. For example,the bit value of the TXOP PS mode field 230 may be configured as 0 toindicate that the TXOP PS mode is not used or allowed and may beconfigured as 1 to indicate that the TXOP PS mode is used or allowed.

It is configured to indicate whether the TXOP PS mode is used andwhether the TXOP PS mode is allowed in accordance with the bit value 0or 1 of the TXOP PS mode field 230 is only an example and the presentinvention is not limited to the above.

The method of the mesh STAs changing the TXOP PS mode using the bit ofthe TXOP PS mode field 230 in the VHT operating mode field 200 accordingto the embodiment of the present invention was described. However, thepresent invention is not limited to the above. The method may be appliedto an AP and an STA of a wireless LAN system such as an infrastructureBSS and an independent BSS (IBSS) as well as the mesh STAs.

For example, when the STA in the wireless LAN system desires to changethe TXOP PS mode thereof, the bit value of the TXOP PS mode field 230 inthe VHT operating mode field 200 is configured as 0 or 1 to indicatethat the TXOP PS mode is used or is not used. That is, the STA maychange the TXOP PS mode thereof using the bit value of the TXOP PS modefield 230 in the VHT operating mode field 200 and may transmit the VHToperating mode notification frame to other STAs to notify the other STAsof the change.

When the AP in the wireless LAN system desires to change whether theTXOP PS mode thereof is allowed, the bit value of the TXOP PS mode field230 in the VHT operating mode field 200 may be configured as 0 or 1 toindicate that the TXOP PS mode is allowed or is not allowed. That is,the AP may change the TXOP PS mode thereof using the bit value of theTXOP PS mode field 230 in the VHT operating mode field 200 and maytransmit the VHT operating mode notification frame to all of the STAs inthe BSS to notify the STAs of the change. At this time, the AP maytransmit the VHT operating mode notification frame to all of the STAs inthe BSS using a broadcast RA.

Hereinafter, a method of exchanging information on the TXOP PS modeamong the mesh STAs using a diagnostic reporting function of the IEEE802.11v standard that provides various functions for managing a wirelessnetwork is provided. In the diagnostic reporting function, the states ofthe STAs on the wireless network may be reported. Diagnostic report onthe states of the STAs is performed by exchanging a diagnostic requestelement and a diagnostic response element. Various diagnosticinformation subelements are included in the diagnostic request elementand the diagnostic response element. The diagnostic informationsubelements include information elements on the PS mode. According tothe present invention, furthermore, a method of reporting information onthe TXOP PS mode is provided.

FIG. 12 is a view illustrating the fields of a PS mode subelementincluded in a diagnostic information subelement for reportinginformation on the TXOP PS mode according to an embodiment of thepresent invention.

Referring to FIG. 12 , the PS mode subelement 600 including informationon the PS mode in the diagnostic information subelement includes asubelement ID 610 for indicating the identifier of a subelement, alength 620 for indicating the length of the PS mode subelement 600, anda PS mode 630 for indicating information on the PS mode.

The PS mode 630 of the PS mode subelement 600 according to theembodiment of the present invention includes a field indicating theinformation on the TXOP PS mode in order to report the information onthe TXOP PS mode of the mesh STAs. The following table 1 illustrates anexample of information included in the PS mode 630 subelement accordingto the present invention.

TABLE 1 Power Save Mode Bit Unknown 0 None 1 PS mode (ReceiveDTIMs = 1)2 PS mode (ReceiveDTIMs = 0) 3 U-APSD 4 S-APSD 5 U-PSMP 6 S-PSMP 7 SMPower Save 8 WNM-Sleep Mode 9 FMS 10 TIM Broadcast 11 TFS 12 TDLS PeerU-APSD 13 TDLS Peer PSM 14 TXOP Power Save 15 Reserved 16~31

The PS mode 630 subelement includes all of the information elementsprovided by the IEEE 802.11v, that is, the other information elementsexcluding the TXOP Power Save element illustrated in the table 1. Inorder to report the information on the TXOP PS mode of the mesh STAsaccording to the embodiment of the present invention, in the PS mode 630of the IEEE 802.11v, one bit among reserved bits 15 to 31 bits isallotted as a bit for indicating the information on the TXOP PS mode.For example, as illustrated in the table 1, a TXOP PS field forreporting the information on the TXOP PS mode of the mesh STAs may beallotted to the 15 bits of the PS mode 630 subelement.

Therefore, after the mesh STAs configure the peer link, when a mesh STAdesires to report the information on the TXOP PS mode thereof or toobtain the information on the TXOP PS mode of another mesh STA,information on whether the TXOP PS mode is used or allowed is configuredusing the bit value of the TXOP PS field in the PS mode subelement andthe diagnostic request element and the diagnostic response element areexchanged so that the information on the TXOP PS mode may be transmittedand received among the mesh STAs.

The method of reporting the information on the TXOP PS mode of the meshSTAs using the bit value of the PS mode 630 field of the PS modesubelement 600 according to the embodiment of the present invention wasdescribed. However, the present invention is not limited to the above.The method may be applied to the AP and the STA of the wireless LANsystem such as the infrastructure BSS and the independent BSS (IBSS) aswell as the mesh STAs.

For example, when the AP or the STA desires to report the information onthe TXOP PS mode thereof or to obtain the information on the TXOP PSmode of another AP or STA, the information on the TXOP PS mode may beconfigured using the value of the TXOP PS field in the PS mode 630 fieldand may be reported by exchanging the diagnostic request element and thediagnostic response element between the APs and the STAs in the BSS. Asdescribed above, according to the present invention, a wireless LAN STAis supported to dynamically change the TXOP PS mode and to exchange theinformation on the TXOP PS mode so that the wireless LAN STA may savepower.

While some exemplary embodiments of the present invention have beendescribed with reference to the accompanying drawings, those skilled inthe art may change and modify the present invention in various wayswithout departing from the essential characteristic of the presentinvention. Accordingly, the disclosed embodiments should not beconstrued to limit the technical spirit of the present invention, butshould be construed to illustrate the technical spirit of the presentinvention. The scope of the technical spirit of the present invention isnot limited by the embodiments, and the scope of the present inventionshould be interpreted based on the following appended claims.Accordingly, the present invention should be construed to cover allmodifications or variations induced from the meaning and scope of theappended claims and their equivalents.

1. A communication method, comprising: transmitting, by a first station,a mesh peering open frame to a second mesh station; and receiving, bythe first station, a mesh peering confirm frame from the second meshstation in response to the mesh peering open frame, wherein the meshpeering open frame includes a very high throughput (VHT) capabilityinformation element, and wherein the VHT capability information elementincludes an information element indicating whether a transmissionopportunity (TXOP) power save mode is supported.
 2. The communicationmethod of claim 1, wherein the VHT capability information elementincludes an information element indicating a maximum MAC protocol dataunit (MPDU) length.
 3. The communication method of claim 1, wherein theVHT capability information element includes an information elementindicating a channel bandwidth supported by the first station.
 4. Thecommunication method of claim 1, wherein the VHT capability informationelement includes an information element indicating whether an encodedpacket is received by a low density parity check (LDPC).
 5. Thecommunication method of claim 1, wherein the VHT capability informationelement includes an information element indicating whether a short guardinterval (GI) is supported.
 6. The communication method of claim 1,wherein the VHT capability information element includes an informationelement indicating whether reception of a Physical Layer ConvergenceProcedure (PLCP) protocol data unit (PPDU) using space time block coding(STBC) is supported,
 7. The communication method of claim 1, wherein themesh peering open frame and the mesh peering confirm frame each includesa VHT operation information element.
 8. The communication method ofclaim 1, wherein the first mesh station performs passive scanning oractive scanning in order to discover the second mesh station beforetransmitting the mesh peering open frame.